2-(pyrimidinecarbonyl)-1,3-cyclohexanediones and their use as herbicidal agents

ABSTRACT

Herbicidal compounds having the formula ##STR1## wherein R 1  is hydrogen, C 1  -C 4  alkyl, phenyl or substituted phenyl; 
     R 2  is hydrogen or C 1  -C 4  alkyl; or 
     R 1  and R 2  together are C 2  -C 5  alkylene; 
     R 3  is hydrogen, C 1  -C 4  alkyl, phenyl or substituted phenyl, with the proviso that R 1  and R 3  are not both phenyl or substituted phenyl; 
     R 4  is hydrogen or C 1  -C 4  alkyl; or 
     R 3  and R 4  together are oxo; 
     R 5  is hydrogen or C 1  -C 4  alkyl; 
     R 6  is hydrogen or C 1  -C 4  alkyl; and 
     R 7  and R 8  independently are (1) hydrogen; (2) halogen; (3) C 1  -C 4  alkyl; (4) C 1  -C 4  alkoxy; (5) trifluoromethoxy; (6) cyano; (7) nitro; (8) C 1  -C 4  haloalkyl; (9) R b  SO n  -- wherein n is the integer 0, 1 or 2; and R b  is (a) C 1  -C 4  alkyl; (b) C 1  -C 4  alkyl substituted with halogen or cyano; (c) phenyl; or (d) benzyl; (10) --NR c  R d  wherein R c  and R d  independently are hydrogen or C 1  -C 4  alkyl; (11) R e  C(O)-- wherein R e  is C 1  -C 4  alkyl or C 1  -C 4  alkoxy; or (12) --SO 2  NR c  R d  wherein R c  and R d  are as defined; and (13) --N(R c )C(O)R d  wherein R c  and R d  are as defined; and their salts.

BACKGROUND OF THE INVENTION

European Patent Application No. 135,191 relats to certain herbicidal compounds that can have the following structural formula ##STR2## wherein R¹ through R⁸ are substantially as defined below.

DESCRIPTION OF THE INVENTION

This invention relates to 2-(pyrimidinecarbonyl)-1,3-cyclohexanediones and their use as herbicides.

One embodiment of this invention is an herbicidal composition comprising an herbicidally active 2-(pyrimidinecarbonyl)-1,3-cyclohexanedione and an inert carrier therefor. The 4- or 6-positions of the 1,3-cyclohexanedione moiety can be substituted with one or two C₁ -C₄ alkyl groups, preferably with methyl groups, although such a substitution is not preferred. The 5-position of the 1,3-cyclohexanedione ring can be substituted with an oxo group when both the 4- and 6-positions each are substituted with two C₁ -C₄ alkyl groups.

Also embodied within the scope of this invention are novel compounds having the following structural formula ##STR3## wherein R¹ is hydrogen; C₁ -C₄ alkyl, preferably methyl; phenyl; or substituted phenyl;

R² is hydrogen or C₁ -C₄ alkyl, preferably methyl; or

R¹ and R² together are C₂ -C₅ alkylene;

R³ is hydrogen; C₁ -C₄ alkyl, preferably methyl; phenyl; or substituted phenyl, with the proviso that R¹ and R³ are not both phenyl or substituted phenyl;

R⁴ is hydrogen or C₁ -C₄ alkyl, preferably methyl; or

R³ and R⁴ together are oxo;

R⁵ is hydrogen or C₁ -C₄ alkyl, preferably methyl;

R⁶ is hydrogen or C₁ -C₄ alkyl, preferably methyl; and

R⁷ and R⁸ independently are (1) hydrogen; (2) halogen, preferably chlorine, fluorine or bromine; (3) C₁ -C₄ alkyl, preferably methyl; (4) C₁ -C₄ alkoxy, preferably methoxy; (5) trifluoromethoxy; (6) cyano; (7) nitro; (8) C₁ -C₄ haloalkyl, more preferably trifluoromethyl; (9) R^(b) SO_(n) -- wherein n is the integer 0, 1 or 2, preferably 2; and

R^(b) is (a) C₁ -C₄ alkyl, preferably methyl;

(b) C₁ -C₄ alkyl substituted with halogen or cyano, preferably chloromethyl, trifluoromethyl or cyanomethyl;

(c) phenyl; or

(d) benzyl;

(10) --NR^(c) R^(d) wherein R^(c) and R^(d) independently are hydrogen or C₁ -C₄ alkyl;

(11) R^(e) C(O)-- wherein R^(e) is C₁ -C₄ alkyl or C₁ -C₄ alkoxy;

(12) --SO₂ NR^(c) R^(d) wherein R^(c) and R^(d) are as defined; or

(13) --N(R^(c))C(O)R^(d) wherein R^(c) and R^(d) are as defined.

Preferably R⁷ is hydrogen, chlorine, fluorine, trifluoromethyl, cyano, C₁ -C₄ alkoxy or C₁ -C₄ thioalkyl. Most preferably, R⁷ is hydrogen. Preferably R⁸ is halogen, cyano, trifluoromethyl, or R^(b) wherein R^(b) is C₁ -C₄ alkyl, preferably methyl or C₁ -C₄ haloalkyl, preferably chloromethyl, difluoromethyl or trifluoromethyl.

The term "C₁ -C₄ alkyl" includes methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl and t-butyl. The term "halogen" includes chlorine, bromine, iodine and fluorine. The terms "C₁ -C₄ alkoxy" includes methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, isobutoxy and t-butoxy. The term "C₁ -C₄ haloalkyl" includes the alkyl groups defined above under C₁ -C₄ alkyl in which one or more hydrogens is replaced by chlorine, bromine, iodine or fluorine.

Salts of the above-described compounds (as defined hereinafter) are included within the scope of the instant invention.

The compounds of this invention can have the following four structural formulae because of tautomerism: ##STR4## wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ are as defined above.

The circled proton on each of the four tautomers is reasonably labile. These protons are acidic and can be removed by reaction with a base to form a salt, including internal salts, having an anion of the following four resonance forms: ##STR5## wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ are as defined above.

Examples of cations of these bases are inorganic cations such as alkali metals, e.g. lithium, sodium and potassium; the alkaline earth metals, e.g. calcium and magnesium or ammonium or organic cations such as substituted ammonium, sulfonium, sulfoxonium or phosphonium wherein the substitutents are aliphatic or aromatic groups, or internal pyrimidinium.

Those skilled in the art will recognize in considering the salts of this invention that varying degrees of association between the anion and cation will exist depending upon the nature of the cation. In some instances with a suitable cation, such as copper, the salt can exist in a chelated form.

The compounds of this invention and their salts are active herbicides of a general type. That is, they are herbicidally effective against a wide range of plant species. The method of controlling undesirable vegetation of the present invention comprises applying an herbicidally effective amount of the above-described compounds or their salts to the area where control is desired.

The compounds of the present invention can be prepared by the following two-step general method.

The process proceeds via the production of an enol ester intermediate as shown in reaction (1). The final product is obtained by rearrangement of the enol ester as shown in reaction (2).

The process is conducted in the presence of a catalytic amount of a source of cyanide anion and/or hydrogen cyanide, together with a molar excess, with respect to the enol ester, of a moderate base.

The two reactions may be conducted as separate steps by isolation and recovery of the enol ester using conventional techniques prior to conducting step (2), or by addition of a cyanide source to the reaction medium after the formation of the enol ester, or in one step by inclusion of the cyanide source at the start of reaction (1). ##STR6## wherein R¹ through R⁸ and moderate base are as defined and Y is halogen, preferably chlorine, C₁ -C₄ alkyl--C(O)--O--, C₁ -C₄ alkoxy--C(O)--O-- or ##STR7## wherein R⁷ and R⁸ in this portion of the molecule are identical with those in the reactant shown above and the moderate base is as defined, preferably tri-C₁ -C₆ alkylamine, alkali metal carbonate or alkali metal phosphate.

Generally, in step (1) mole amounts of the dione and substituted pyrimidinecarbonyl reactant are used, along with a mole amount or excess of the base. The two reactants are combined in an organic solvent such as methylene chloride, toluene, ethyl acetate or dimethylformamide. The base or pyrimidinearbonyl reactant preferably is added to the reaction mixture with cooling. The mixture is stirred at 0° C.-50° C. until the reaction is substantially complete. ##STR8## wherein the moderate base and R¹ through R⁸ are as defined above.

Generally, in step (2) a mole of the enol ester intermediate is reacted with 1 to 4 moles of the moderate base, preferably about 2 moles of moderate base and from 0.01 mole to about 0.5 mole or higher, preferably about 0.01-0.1 mole of the cyanide source. The mixture is stirred in a reaction pot until the rearrangement is substantially complete at a temperature below 50° C., preferably about 20° C. to about 40° C., and the desired product is recovered by conventional techniques.

The term "cyanide source" refers to a substance or substances which under the rearrangement conditions consists of or generates hydrogen cyanide and/or cyanide anion.

Preferred cyanide sources are alkali metal cyanides such as sodium and potassium cyanide; cyanohydrins of methyl alkyl ketones having from 1-4 carbon atoms in the alkyl groups, such as acetone or methyl isobutyl ketone cyanohydrins; benzaldehyde cyanohydrin; cyanohydrins of C₂ -C₅ aliphatic aldehydes such as acetaldehyde cyanohydrin, propionaldehyde propionaldehyde cyanohydrin, etc.; cyclohexanone cyanohydrin; lactonitrile; zinc cyanide; di- and tri-(lower alkyl) silyl cyanides, notably dimethyl- and trimethyl-silyl cyanide; potassium ferricyanide; and hydrogen cyanide itself. Hydrogen cyanide is considered most advantageous as it produces relatively rapid reaction and is inexpensive. Among cyanohydrins the preferred cyanide source is acetone cyanohydrin.

The cyanide source is used in an amount up to about 50 mole percent based on the enol ester. It may be used in as little as about 1 mole percent to produce an acceptable rate of reaction at about 40° C. on a small scale. Larger scale reactions give more reproducible results with slightly higher catalyst levels of about 2 mole percent. Generally about 1-10 mole % of the cyanide source is preferred.

The process is conducted with a molar excess, with respect to the enol ester, of a moderate base. By the term "moderate base" is meant a substance which acts as a base yet whose strength or activity as a base lies between that of strong bases such as hydroxides (which could cause hydrolysis of the enol ester) and that of weak bases such as N,N-dimethylaniline (which would not function effectively). Moderate bases suitable for use in this embodiment include both organic bases, e.g., trialkylamines such as triethylamine and inorganic bases such as alkali metal carbonates and phosphates. Suitable inorganic bases include potassium carbonate and trisodium phosphate.

The base is used in an amount of from about 1 to about 4 moles per mole of enol ester, preferably about 2 moles per mole.

When the cyanide source is an alkali metal cyanide, particularly potassium cyanide, a phase transfer catalyst may be included in the reaction. Particularly suitable phase transfer catalysts are the crown ethers.

A number of different solvents are useful in this process, depending on the nature of the acid halide or the acylated product. A preferred solvent for this reaction is 1,2-dichloroethane. Other solvents which may be employed, depending on the reactants or products include toluene, acetonitrile, methylene chloride, ethyl acetate, dimethylformamide, and methyl isobutyl ketone (MIBK).

In general, depending on the nature of the reactants and the cyanide source, the rearrangment may be conducted at temperatures up to about 50° C.

The above described substituted pyrimidinecarbonyl chlorides can be prepared from the corresponding substituted pyrimidinecarboxylic acids according to the teaching of Reagents for Organic Synthesis, Vol. I, L. F. Fieser and M. Fieser, pp. 767-769 (1967). ##STR9## wherein R⁷ and R⁸ are as previously defined.

The following example teaches the synthesis of a representative compound of this invention.

EXAMPLE 1 2-(5'-Bromo-2'-methylthiopyrimidine-4-carbonyl)-1,3-cyclohexanedione ##STR10##

1,3-Cyclohexanedione [1.3 grams (g), 12 mmol) and 5-bromo-2-methylthiopyrimidine-4-carbonyl chloride (3.2 g, 12 mmol) were dissolved in 15 milliliters (ml) acetonitrile. Triethylamine (4.2 ml, 30 mmol) was added and the resulting solution stirred for 10 minutes at room temperature under an atmosphere of nitrogen. Acetone cyanohydrin (1.0 ml, 11 mmol) was added and the mixture was stirred at room temperature for 3 hours. After dilution with ethyl acetate, the solution was washed with dilute hydrochloric acid and extracted with 5% potassium carbonate solution. The basic extract was acidified with concentrated hydrochloric acid and extracted with methylene chloride. The methylene chloride extract was dried over anhydrous magnesium sulfate and concentrated under vacuum to yield 2.7 g of a brown solid (m.p. 140°-141° C.) that was identified as the desired product by nuclear magnetic resonance spectroscopy, infrared spectroscopy and mass spectroscopy.

The following Tables 1 and 2 show certain selected compounds that are preparable according to the procedure described hereto. Compound numbers are assigned to each compound and are used throughout the remainder of the application.

                  TABLE 1                                                          ______________________________________                                          ##STR11##                                                                     Cmpd.                                             m.p.                         No.   R.sup.1                                                                               R.sup.2                                                                               R.sup.3                                                                            R.sup.4                                                                            R.sup.5                                                                             R.sup.6                                                                             R.sup.7                                                                               R.sup.8                                                                             °C.                   ______________________________________                                                                                           2                            1     H      H      H   H   H    H    4-Cl   H    oil                          2     CH.sub.3                                                                              CH.sub.3                                                                              H   H   H    H    2-SCH.sub.3                                                                           5-Cl oil                          .sup. 3.sup.a                                                                        H      H      H   H   H    H    2-SCH.sub.3                                                                           5-Br 140-                                                                           141                          4     CH.sub.3                                                                              CH.sub.3                                                                              O     CH.sub.3                                                                            CH.sub.3                                                                            2-SCH.sub. 3                                                                          5-Br gum                            ______________________________________                                          .sup.a Prepared in Example I.                                            

                                      TABLE 2                                      __________________________________________________________________________      ##STR12##                                                                     Cmpd. No.                                                                             R.sup.1                                                                           R.sup.2                                                                           R.sup.3                                                                           R.sup.4                                                                           R.sup.5                                                                          R.sup.6                                                                          R.sup.7                                                                              R.sup.8                                                                             m.p. °C.                              __________________________________________________________________________     5      H  H  H  H  H H 2-OCH.sub.3                                                                          4-OCH.sub.3                                                                         oil                                          6      H  H  H  H  H H 2-SCH.sub.3                                                                          4-CH.sub.3                                                                          90-91                                        7      CH.sub.3                                                                          CH.sub.3                                                                          H  H  H H 2-SCH.sub.3                                                                          4-CH.sub.3                                                                          oil                                          8      H  H  CH.sub.3                                                                          CH.sub.3                                                                          H H 2-SCH.sub.3                                                                          4-OCH.sub.3                                                                         102-104                                      9      CH.sub.3                                                                          CH.sub.3                                                                          H  H  H H 2-SCH.sub.3                                                                          4-OCH.sub.3                                                                         oil                                          10     H  H  H  H  H H 2-N(CH.sub. 3).sub.2                                                                 4-CH.sub.3                                                                          93-95                                        11     H  H  H  H  H H 2-OCH.sub.3                                                                          4-CH.sub.3                                                                          102-103                                      12     H  H  H  H  H H 2-OCH.sub.3                                                                          4-CF.sub.3                                                                          oil                                          13     H  H  H  H  H H 2-C.sub.3 H.sub.7                                                                    4-CH.sub.3                                                                          50-55                                        14     CH.sub.3                                                                          CH.sub.3                                                                          H  H  H H 2-C.sub.3 H.sub.7                                                                    4-CH.sub.3                                                                          oil                                          15     H  H  H  H  H H 2-iPr 4-CH.sub.3                                                                          65-70                                        16     CH.sub.3                                                                          CH.sub.3                                                                          H  H  H H 2-iPr 4-CH.sub.3                                                                          oil                                          17     H  H  H  H  H H 2-C.sub.2 H.sub.5                                                                    4-CH.sub.3                                                                          72-80                                        18     H  H  H  H  H H 2-CF.sub.3                                                                           4-CH.sub.3                                                                          90-85                                        19     H  H  H  H  H H 2-C.sub.2 H.sub.5                                                                    4-CF.sub.3                                                                          oil                                          20     H  H  H  H  H H 2-CCl.sub.3                                                                          4-CH.sub.3                                                                          125-128                                      __________________________________________________________________________

HERBICIDAL SCREENING TESTS

As previously mentioned, the herein described compounds produced in the above-described manner are phytotoxic compounds which are useful and valuable in controlling various plant species. Selected compounds of this invention were tested as herbicides in the following manner.

Pre-emergence herbicide test.

On the day preceding treatment, seeds of seven different weed species are planted in loamy sand soil in individual rows using one species per row across the width of a flat. The seeds used are green foxtail (FT) (Setaria viridis), watergrass (WG) (Echinochloa crusgalli), wild oat (WO) (Avena fatua), annual morningglory (AMG) (Ipomoea lacunosa), velvetleaf (VL) (Abutilon theophrasti), Indian mustard (MD) (Brassica juncea), and yellow nutsedge (YNG) (Cyperus esculentus). Ample seeds are planted to give about 20 to 40 seedlings per row, after emergence, depending upon the size of the plants.

Using an analytical balance, 600 milligrams (mg) of the compound to be tested are weighed out on a piece of glassine weighing paper. The paper and compound are placed in a 60 milliliter (ml) wide-mouth clear bottle and dissolved in 45 ml of acetone or substituted solvent. Eighteen ml of this solution are transferred to a 60 ml wide-mouth clear bottle and diluted with 22 ml of a water and acetone mixture (19:1) containing enough polyoxyethylene sorbitan monolaurate emulsifier to give a final solution of 0.5% (v/v). The solution is then sprayed on a seeded flat on a linear spray table calibrated to deliver 80 gallons per acre (748 L/ha). The application rate is 4 lb/acre (4.48 Kg/ha).

After treatment, the flats are placed in the greenhouse at a temperature of 70° to 80° F. and watered by sprinkling. Two weeks after treatment, the degree of injury or control is determined by comparison with untreated check plants of the same age. The injury rating from 0 to 100% is recorded for each species as percent control with 0% representing no injury and 100% representing complete control.

The results of the tests are shown in the following Table 3.

                  TABLE 3                                                          ______________________________________                                         Pre-Emergence Herbicidal Activity                                              Application Rate - 4.48 kg/ha                                                  Cmpd.                                                                          No.    FT      WG     WO    AMG   VL    MD   YNS                               ______________________________________                                          1     0       0      0     0     0     0    0                                  2     0       50     0     0     100   0    80                                 3     0       30     0     5     100   80   80                                 4     0       90     0     20    100   0    0                                  5     100     100    100   100   100   100  80                                 6     30      40     5     5     80    100  80                                 7     5       10     0     0     100   20   80                                 8     0       0      0     5     0     10   0                                  9     0       0      0     5     0     10   10                                10     100     90     10    40    100   100  80                                11     40      100    30    90    100   100  80                                12     100     100    60    100   100   100  80                                13     100     100    90    90    100   100  80                                14     100     100    80    80    100   100  80                                15     100     100    90    80    100   100  80                                16     100     100    85    90    100   100  80                                17     100     100    85    80    100   100  80                                18     100     100    50    100   100   100  80                                19     100     100    50    100   100   100  80                                20     100     100    20    40    100   100  30                                ______________________________________                                    

Post-Emergence Herbicide Test:

This test is conducted in an identical manner to the testing procedure for the pre-emergence herbicide test, except the seeds of the seven different weed species are planted 10-12 days before treatment. Also, watering of the treated flats is confined to the soil surface and not to the foliage of the sprouted plants.

The results of the post-emergence herbicide test are reported in Table 4.

                  TABLE 4                                                          ______________________________________                                         Post-Emergence Herbicidal Activity                                             Application Rate - 4.48 kg/ha                                                  Cmpd.                                                                          No.    FT      WG     WO    AMG   VL    MD   YNS                               ______________________________________                                          1     0       0      0     0     0     0    10                                 2     0       10     0     0     90    10   0                                  3     0       10     0     20    90    0    0                                  4     0       50     0     10    80    0    30                                 5     70      80     80    20    90    90   65                                 6     30      30     0     20    80    50   80                                 7     30      50     0     20    50    10   30                                 8     0       0      0     0     0     5    0                                  9     0       0      0     0     20    10   5                                 10     30      60     30    40    90    60   70                                11     50      50     20    50    50    50   20                                12     60      60     50    80    80    80   70                                13     80      80     40    80    100   100  60                                14     80      80     40    85    100   80   60                                15     90      80     30    80    100   90   40                                16     100     85     90    85    100   90   70                                17     90      80     40    80    95    95   70                                18     100     100    30    100   100   100  30                                19     80      100    20    100   100   100  70                                20     100     90     10    20    100   90   30                                ______________________________________                                    

The compounds of the present invention and their salts are useful as herbicides and can be applied in a variety of ways at various concentrations. In practice, the compounds or salts are formulated into herbicidal compositions, by admixture, in herbicidally effective amounts, with the adjuvants and carriers normally employed for facilitating the dispersion of active ingredients for agricultural applications, recognizing the fact that the formulation and mode of application of a toxicant may affect the activity of the materials in a given application. Thus, these active herbicidal compounds or salts can be formulated as granules of relatively large particle size, as wettable powders, as emulsifiable concentrates, as powdery dusts, as flowables, as solutions or as any of several other known types of formulations, depending upon the desired mode of application. These formulations may contain as little as about 0.5% to as much as about 95% or more by weight of active ingredient. A herbicidally effective amount depends upon the nature of the seeds or plants to be controlled and the rate of application varies from about 0.01 to approximately 10 pounds per acre, preferably from about 0.02 to about 4 pounds per acre.

Wettable powders are in the form of finely divided particles which disperse readily in water or other dispersants. The wettable powder is ultimately applied to the soil either as a dry dust or as a dispersion in water or other liquid. Typical carriers for wettable powders include fuller's earth, kaolin clays, silicas and other readily wet organic or inorganic diluents. Wettable powders normally are prepared to contain about 5% to about 95% of the active ingredient and usually also contain a small amount of wetting, dispersing, or emulsifying agent to facilitate wetting and dispersion.

Emulsifiable concentrates are homogeneous liquid compositions which are dispersible in water or other dispersant, and may consist entirely of the active compound of salt with a liquid or solid emulsifying agent, or may also contain a liquid carrier, such as xylene, heavy aromatic naphthal, isophorone and other non-volatile organic solvents. For herbicidal application, these concentrates are dispersed in water or other liquid carrier and normally applied as a spray to the area to be treated. The percentage by weight of the essential active ingredient may vary according to the manner in which the composition is to be applied, but in general comprises about 0.5% to 95% of active ingredient by weight of the herbicidal composition.

Granular formulations wherein the toxicant is carried on relatively coarse particles, are usually applied without dilution to the area in which suppression of vegetation is desired. Typical carriers for granular formulations include sand, Fuller's earth, attapulgite clay, bentonite clays, montmorillonite clay, vermiculite, perlite and other organic or inorganic materials which absorb or which may be coated with the toxicant. Granular formulations normally are prepared to contain from about to about 25% of active ingredients which may include surface-active agents such heavy aromatic naphthas, kerosene or other petroleum fractions, or vegetable oils; and/or stickers such as destrins, glue or synthetic resins.

Typical wetting, dispersing or emulsifying agents used in agricultural formulations include, for example, the alkyl and alkylaryl sulfonates and sulfates and their salts; polyhydric alcohols; polyethoxylated alcohols; esters and fatty amines; and other types of surface-active agents, many of which are available in commerce. The surface-active agent, when used, normally comprises from 0.1% to 15% by weight of the herbicidal composition.

Dusts, which are free-flowing admixtures of the active ingredient with finely divided solids such as talc, clays, flours and other organic and inorganic solids which act as dispersants and carriers for the toxicant, are useful formulations for soil-incorporating application.

Pastes, which are homogeneous suspensions of a finely divided solid toxicant in a liquid carrier such as water or oil, are employed for specific purposes. These formulations normally contain about 5% to about 95% of active ingredient by weight, and may also contain small amounts of a wetting, dispersing or emulsifying agent to facilitate dispersion. For application, the pastes are normally diluted and applied as a spray to the area to be affected.

Other useful formulations for herbicidal applications include simple solutions of the active ingredient in a dispersant in which it is completely soluble at the desired concentration, such as acetone, alkylated naphthalenes, xylene and other organic solvents. Pressurized sprays, typically aerosols, wherein the active ingredient is dispersed in finely-divided form as a result of vaporization of a low boiling dispersant solvent carrier, such as the Freons, may also be used.

The phytotoxic compositions of this invention can be applied to the plants in the conventional manner. Thus, the dust and liquid compositions can be applied to the plant by the use of power-dusters, boom and hand sprayers and spray dusters. The compositions can also be applied from airplanes as a dust or a spray or by rope wick applications because they are effective in very low dosages. In order to modify or control growth of germinating seeds or emerging seedlings, as a typical example, the dust and liquid compositions can be applied to the soil according to conventional methods and can be distributed in the soil to a depth of at least 1/2 inch below the soil surface. It is not necessary that the phytotoxic compositions be mechanically admixed with the soil particles since these compositions can also be applied merely by spraying or sprinkling the surface of the soil. The phytotoxic compositions of this invention can also be applied by addition to irrigation water supplied to the field to be treated. This method of application permits the penetration of the compositions into the soil as the water is absorbed therein. Dust compositions, granular compositions or liquid formulations applied to the surface of the soil can be distributed below the surface of the soil by conventional means such as discing, dragging or mixing operations. In the following examples the herbicidal compound can be substituted with the herbicidal salt of the compound.

EMULSIFIABLE CONCENTRATE FORMULATIONS

    ______________________________________                                         General Formula with Ranges                                                                     Specific Formula                                              ______________________________________                                         Herbicidal compound                                                                         5-55    herbicidal compound                                                                            24                                        surfactant(s)                                                                               5-25    proprietary blend of oil-                                                                      10                                        solvent(s)   20-90   soluble sulfonates and                                                 100%    polyoxyethylene ethers                                                         polar solvent   27                                                             petroleum hydrocarbon                                                                          39                                                                              100%                                     ______________________________________                                    

WETTABLE POWDER FORMULATIONS

    ______________________________________                                         herbicidal compound                                                                          3-90   herbicidal compound                                                                            80                                        wetting agent                                                                               0.5-2   sodium dialkyl    0.5                                     dispersing agent                                                                            1-8     naphthalene sulfonate                                     diluent(s)   8.5-87  sodium lignosulfonate                                                                           7                                                     100%    attapulgite clay                                                                                 12.5                                                                          100%                                     ______________________________________                                    

EXTRUDED GRANULAR FORMULATIONS

    ______________________________________                                         herbicidal compound                                                                         1-20    herbicidal compound                                                                            10                                        binding agent                                                                               0-10    lignin sulfonate                                                                                5                                        diluent(s)   70-99   calcium carbonate                                                                              85                                                     100%                     100%                                     ______________________________________                                    

FLOWABLE FORMULATIONS

    __________________________________________________________________________     herbicidal compound                                                                        20-70 herbicidal compound                                                                         45                                              surfactant(s)                                                                              1-10  polyoxyethylene ether                                                                        5                                              suspending agent(s)                                                                        0.05-1                                                                               attagel         0.05                                         antifreeze agent                                                                           1-10  propylene glycol                                                                            10                                              antimicrobial agent                                                                        1-10  1,2-benzisothiazoline-3-one                                                                    0.03                                         antifoam agent                                                                             0.1-1 silicone defoamer                                                                              0.02                                         solvent     7.95-77.85                                                                           water          39.9                                                      100%                100%                                           __________________________________________________________________________

When salts are used as the active ingredient in the herbicidal compositions of this invention it is recommended to use salts that are agriculturally acceptable.

The phytotoxic compositions of this invention can also contain other additives, for example, fertilizers, other herbicides and other pesticides, used as adjuvant or in combination with any of the above-described adjuvants. Fertilizers useful in combination with the active ingredients include, for example, ammonium nitrate, urea and superphosphate. 

What is claimed is:
 1. Compounds of the formula ##STR13## wherein R¹ is hydrogen, C₁ -C₄ alkyl or phenyl;R² is hydrogen or C₁ -C₄ alkyl; or R¹ and R² together are C₂ -C₅ alkylene; R³ is hydrogen, C₁ -C₄ alkyl or phenyl, with the proviso that R¹ and R³ are not both phenyl; R⁴ is hydrogen or C₁ -C₄ alkyl; or R³ and R⁴ together are oxo; R⁵ is hydrogen or C₁ -C₄ alkyl; R⁶ is hydrogen or C₁ -C₄ alkyl; and R⁷ and R⁸ independently are (1) hydrogen; (2) halogen; (3) C₁ -C₄ alkyl; (4) C₁ -C₄ alkoxy; (5) trifluoromethoxy; (6) cyano; (7) nitro; (8) C₁ -C₄ haloalkyl; (9) R^(b) SO_(n) -- wherein n is the integer 0, 1 or 2; and R^(b) is (a) C₁ -C₄ alkyl; (b) C₁ -C₄ alkyl substituted with halogen or cyano; (c) phenyl; or (d) benzyl; (10) --NR^(c) R^(d) wherein R^(c) and R^(d) independently are hydrogen or C₁ -C₄ alkyl; (11) R^(e) C(O)-- wherein R^(e) is C₁ -C₄ alkyl or C₁ -C₄ alkoxy; or (12) --SO₂ NR^(c) R^(d) wherein R^(c) and R^(d) are as defined; and (13) --N(R^(c))C(O)R^(d) wherein R^(c) and R^(d) are as defined; and their herbicidally acceptable salts.
 2. The compounds of claim 1 wherein R¹, R², R³, R⁴, R⁵ and R⁶ are hydrogen or methyl; R⁷ and R⁸ independently are (1) hydrogen; (2) halogen; (3) C₁ -C₄ alkyl; (4) C₁ -C₄ alkoxy; (5) trifluoromethoxy; (6) cyano; (7) nitro; (8) C₁ -C₄ haloalkyl; (9) R^(b) SO_(n) -- wherein n is the integer 0, 1 or 2; and R^(b) is (a) C₁ -C₄ alkyl; (b) C₁ -C₄ alkyl substituted with halogen or cyano; (c) phenyl; or (d) benzyl; (10) --NR^(c) R^(d) wherein R^(c) and R^(d) independently are hydrogen or C₁ -C₄ alkyl; (11) R^(e) C(O)-- wherein R^(e) is C₁ -C₄ alkyl or C₁ -C₄ alkoxy; or (12) SO₂ NR^(c) R^(d) wherein R^(c) and R^(d) are as defined; or (13) --N--(R^(c))C(O)R^(d) wherein R^(c) and R^(d) are as defined.
 3. The compounds of claim 2 wherein R⁷ and R⁸ are independently are hydrogen; chlorine; fluorine; bromine; methyl; C₁ -C₄ alkoxy; trifluoromethoxy; cyano; nitro; trifluoromethyl; R^(b) SO_(n) -- wherein n is the integer 0 or 2 and R^(b) is methyl, chloromethyl, trifluoromethyl; ethyl or n-propyl, R^(e) C(O)-- where R^(e) is C₁ -C₄ alkyl; or SO₂ NR^(c) R^(d) wherein R^(c) and R^(d) are as defined.
 4. The compounds of claim 2 wherein the pyrimidinecarbonyl moiety is a pyrmidine-5-carbonyl moiety.
 5. The compound of claim 4 wherein R¹ is hydrogen; R² is hydrogen; R³ is hydrogen; R⁴ is hydrogen; R⁵ is hydrogen; R⁶ is hydrogen; R⁷ is 2-methoxy; and R⁸ is 4-methoxy.
 6. The compound of claim 4 wherein R¹ is hydrogen; R² is hydrogen; R³ is hydrogen; R⁴ is hydrogen; R⁵ is hydrogen; R⁶ is hydrogen; R⁷ is 2-dimethylamino; and R⁸ is 4-methyl.
 7. The compound of claim 4 wherein R¹ is hydrogen; R² is hydrogen; R³ is hydrogen; R⁴ is hydrogen; R⁵ is hydrogen; R⁶ is hydrogen; R⁷ is 2-methoxy; and R⁸ is 4-methyl.
 8. The compound of claim 4 wherein R¹ is hydrogen; R² is hydrogen; R³ is hydrogen; R⁴ is hydrogen; R⁵ is hydrogen; R⁶ is hydrogen; R⁷ is 2-methoxy; and R⁸ is 4-trifluoromethyl.
 9. A method of controlling undesirable vegetation consisting of applying to the area where control is desired, a herbicidally effective amount of a compound having the formula ##STR14## wherein R¹ is hydrogen, C₁ -C₄ alkyl or phenyl;R² is hydrogen or C₁ -C₄ alkyl; or R¹ and R² together are C₂ -C₅ alkylene; R³ is hydrogen, C₁ -C₄ alkyl or phenyl, with the proviso that R¹ and R³ are not both phenyl; R⁴ is hydrogen or C₁ -C₄ alkyl; or R³ and R⁴ together are oxo; R⁵ is hydrogen or C₁ -C₄ alkyl; R⁶ is hydrogen or C₁ -C₄ alkyl; and R⁷ and R⁸ independently are (1) hydrogen; (2) halogen; (3) C₁ -C₄ alkyl; (4) C₁ -C₄ alkoxy; (5) trifluoromethoxy; (6) cyano; (7) nitro; (8) C₁ -C₄ haloalkyl; (9) R^(b) SO_(n) -- wherein n is the integer 0, 1 or 2; and R^(b) is (a) C₁ -C₄ alkyl; (b) C₁ -C₄ alkyl substituted with halogen or cyano; (c) phenyl; or (d) benzyl; (10) --NR^(c) R^(d) wherein R^(c) and R^(d) independently are hydrogen or C₁ -C₄ alkyl; (11) R^(e) C(O)-- wherein R^(e) is C₁ -C₄ alkyl or C₁ -C₄ alkoxy; or (12) --SO₂ NR^(c) R^(d) wherein R^(c) and R^(d) are as defined; and (13) --N(R^(c))C(O)R^(d) wherein R^(c) and R^(d) are as defined; and their herbicidally acceptable salts.
 10. The method of claim 9 wherein R¹, R², R³, R⁴, R⁵ and R⁶ are hydrogen or methyl; R⁷ and R⁸ independently are (1) hydrogen; (2) halogen; (3) C₁ -C₄ alkyl; (4) C₁ -C₄ alkoxy; (5) trifluoromethoxy; (6) cyano; (7) nitro; (8) C₁ -C₄ haloalkyl; (9) R^(b) SO_(n) -- wherein n is the integer 0, 1 or 2; and R^(b) is (a) C₁ -C₄ alkyl; (b) C₁ -C₄ alkyl substituted with halogen or cyano; (c) phenyl; or (d) benzyl; (10) --NR^(c) R^(d) wherein R^(c) and R^(d) independently are hydrogen or C₁ -C₄ alkyl; (11) R^(e) C(O)-- wherein R^(e) is C₁ -C₄ alkyl or C₁ -C₄ alkoxy; or (12) SO₂ NR^(c) R^(d) wherein R^(c) and R^(d) are as defined; or (13) --N--(R^(c))C(O)R^(d) wherein R^(c) and R^(d) are as defined.
 11. The method of claim 10 wherein R⁷ and R⁸ are independently are hydrogen; chlorine; fluorine; bromine; methyl; C₁ -C₄ alkoxy; trifluoromethoxy; cyano; nitro; trifluoromethyl; R^(b) SO_(n) -- wherein n is the integer 0 or 2 and R^(b) is methyl, chloromethyl, trifluoromethyl; ethyl or n-propyl, R^(e) C(O)-- where R^(e) is C₁ -C₄ alkyl; or SO₂ NR^(c) R^(d) wherein R^(c) and R^(d) are as defined.
 12. The method of claim 10 wherein the pyrimidinecarbonyl moiety is a pyrimidine-5-carbonyl moiety.
 13. The method of claim 12 wherein R¹ is hydrogen; R² is hydrogen; R³ is hydrogen; R⁴ is hydrogen; R⁵ is hydrogen; R⁶ is hydrogen; R⁷ is 2-methoxy; and R⁸ is 4-methoxy.
 14. The method of claim 12 wherein R¹ is hydrogen; R² is hydrogen; R³ is hydrogen; R⁴ is hydrogen; R⁵ is hydrogen; R⁶ is hydrogen; R⁷ is 2-dimethylamino; and R⁸ is 4-methyl.
 15. The method of claim 12 wherein R¹ is hydrogen; R² is hydrogen; R³ is hydrogen; R⁴ is hydrogen; R⁵ is hydrogen; R⁶ s hydrogen; R⁷ is 2-methoxy; and R⁸ is 4-methyl.
 16. The method of claim 12 wherein R¹ is hydrogen; R² is hydrogen; R³ is hydrogen; R⁴ is hydrogen; R⁵ is hydrogen; R⁶ is hydrogen; R⁷ is 2-methoxy; and R⁸ is 4-trifluoromethyl.
 17. A herbicidal composition consisting of a herbicidally active 2-(substituted pyrimidinecarbonyl)-1,3-cyclohexanedione or a salt thereof and an inert carrier therefor.
 18. The herbicidal composition of claim 17 wherein the 2-(substituted pyrimidinecarbonyl)-1,3-cyclohexanedione is a compound of the formula ##STR15## wherein R¹ is hydrogen, C₁ -C₄ alkyl or phenyl;R² is hydrogen or C₁ -C₄ alkyl; or R¹ and R² together are C₂ -C₅ alkylene; R³ is hydrogen, C₁ -C₄ alkyl or phenyl, with the proviso that R¹ and R³ are not both phenyl or substituted phenyl; R⁴ is hydrogen or C₁ -C₄ alkyl; or R³ and R⁴ together are oxo; R⁵ is hydrogen or C₁ -C₄ alkyl; R⁶ is hydrogen or C₁ -C₄ alkyl; and R⁷ and R⁸ independently are (1) hydrogen; (2) halogen; (3) C₁ -C₄ alkyl; (4) C₁ -C₄ alkoxy; (5) trifluoromethoxy; (6) cyano; (7) nitro; (8) C₁ -C₄ haloalkyl; (9) R^(b) SO_(n) -- wherein n is the integer 0, 1 or 2; and R^(b) is (a) C₁ -C₄ alkyl; (b) C₁ -C₄ alkyl substituted with halogen or cyano; (c) phenyl; or (d) benzyl; (10) --NR^(c) R^(d) wherein R^(c) and R^(d) independently are hydrogen or C₁ -C₄ alkyl; (11) R^(e) C(O)-- wherein R^(e) is C₁ -C₄ alkyl or C₁ -C₄ alkoxy; or (12) --SO₂ NR^(c) R^(d) wherein R^(c) and R^(d) are as defined; and (13) --N(R^(c))C(O)R^(d) wherein R^(c) and R^(d) are as defined; and their herbicidally acceptable salts.
 19. The composition of claim 18 wherein R¹, R², R³, R⁴, R⁵ and R⁶ are hydrogen or methyl; R⁷ and R⁸ independently are (1) hydrogen; (2) halogen; (3) C₁ -C₄ alkyl; (4) C₁ -C₄ alkoxy; (5) trifluoromethoxy; (6) cyano; (7) nitro; (8) C₁ -C₄ haloalkyl; (9) R^(b) SO_(n) -- wherein n is the integer 0, 1 or 2; and R^(b) is (a) C₁ -C₄ alkyl; (b) C₁ -C₄ alkyl substituted with halogen or cyano; (c) phenyl; or (d) benzyl; (10) --NR^(c) R^(d) wherein R^(c) and R^(d) independently are hydrogen or C₁ -C₄ alkyl; (11) R^(e) C(O)-- wherein R^(e) is C₁ -C₄ alkyl or C₁ -C₄ alkoxy; or (12) SO₂ NR^(c) R^(d) wherein R^(c) and R^(d) are as defined; or (13) --N--(R^(c))C(O)R^(d) wherein R^(c) and R^(d) are as defined.
 20. The composition of claim 19 wherein R⁷ and R⁸ are independently are hydrogen; chlorine; fluorine; bromine; methyl; C₁ -C₄ alkoxy; trifluoromethoxy; cyano; nitro; trifluoromethyl; R^(b) SO_(n) -- wherein n is the integer 0 or 2 and R^(b) is methyl, chloromethyl, trifluoromethyl; ethyl or n-propyl, R^(e) C(O)-- where R^(e) is C₁ -C₄ alkyl; or SO₂ NR^(c) R^(d) wherein R^(c) and R^(d) are as defined.
 21. The composition of claim 19 wherein the pyrimidinecarbonyl moiety is a pyrmidine-5-carbonyl moiety.
 22. The composition of claim 21 wherein R¹ is hydrogen; R² is hydrogen; R³ is hydrogen; R⁴ is hydrogen; R⁵ is hydrogen; R⁶ is hydrogen; R⁷ is 2-methoxy; and R⁸ is 4-methoxy.
 23. The composition of claim 21 wherein R¹ is hydrogen; R² is hydrogen; R³ is hydrogen; R⁴ is hydrogen; R⁵ is hydrogen; R⁶ is hydrogen; R⁷ is 2-dimethylamino; and R⁸ is 4-methyl.
 24. The composition of claim 21 wherein R¹ is hydrogen; R² is hydrogen; R³ is hydrogen; R⁴ is hydrogen; R⁵ is hydrogen; R⁶ is hydrogen; R⁷ is 2-methoxy; and R⁸ is 4-methyl.
 25. The composition of claim 21 wherein R¹ is hydrogen; R² is hydrogen; R³ is hydrogen; R⁴ is hydrogen; R⁵ is hydrogen; R⁶ is hydrogen; R⁷ is 2-methoxy; and R⁸ is 4-trifluoromethyl.
 26. The method of controlling undesirable vegetation comprising applying to the area where control is desired, a herbicidal composition comprising a herbicidally active 2-(pyrimidinecarbonyl)-1,3-cyclohexanedione or its herbicidally acceptable salt and an inert carrier therefor.
 27. A compound of the structural formula ##STR16## wherein R¹ is hydrogen, C₁ -C₄ alkyl or phenyl;R² is hydrogen or C₁ -C₄ alkyl; or R¹ and R² together are C₂ -C₅ alkylene; R³ is hydrogen, C₁ -C₄ alkyl or phenyl, with the proviso that R¹ and R³ are not both phenyl; R⁴ is hydrogen or C₁ -C₄ alkyl; or R³ and R⁴ together are oxo; R⁵ is hydrogen or C₁ -C₄ alkyl; R⁶ is hydrogen or C₁ -C₄ alkyl; and R⁷ and R⁸ independently are (1) hydrogen; (2) halogen; (3) C₁ -C₄ alkyl; (4) C₁ -C₄ alkoxy; (5) trifluoromethoxy; (6) cyano; (7) nitro; (8) C₁ -C₄ haloalkyl; (9) R^(b) SO_(n) -- wherein n is the integer 0, 1 or 2; and R^(b) is (a) C₁ -C₄ alkyl; (b) C₁ -C₄ alkyl substituted with halogen or cyano; (c) phenyl; or (d) benzyl; (10) --NR^(c) R^(d) wherein R^(c) and R^(d) independently are hydrogen or C₁ -C₄ alkyl; (11) R^(e) C(O)-- wherein R^(e) is C₁ -C₄ alkyl or C₁ -C₄ alkoxy; or (12) --SO₂ NR^(c) R^(d) wherein R^(c) and R^(d) are as defined; and (13) --N(R^(c))C(O)R^(d) wherein R^(c) and R^(d) are as defined. 